Although Jeb Bush has yet to officially join the increasingly crowded field of Republican presidential wannabes, the former Florida governor’s Super PAC has firmly established him as the leading candidate of the Republican establishment in 2016.

But Super PACs are a double-edged sword for Bush. If he ultimately fails to win the Republican nomination, Super PACs will be a major reason why.

By historical standards, Bush’s fund-raising success is astounding. Right to Rise, the Bush Super PAC, has raised more money in the first quarter of 2015 – nearly $100 million – than any Republican campaign organization in history, at least, according to Bush himself. The $100 million figure shatters the previous record, held, ironically enough, by Jeb’s older brother, George W Bush, who in the first quarter of 1999 raised a then-record $36 million.

But George’s $36 million meant a lot more 16 years ago than Jeb’s $100 million means today. In 1999, George Bush’s fund-raising prowess dissuaded other major candidates from running against him, including Lamar Alexander, Jack Kemp and Dan Quayle. The only serious primary challenge Bush faced came from John McCain. Bush’s financial advantages ultimately overwhelmed McCain, who dropped out in early March 2000.

What Jeb Bush faces in today’s presidential race

Jeb Bush faces a far different political landscape. Today, the Republican field is rapidly expanding even as Bush sets new fund-raising records.

When George W Bush ran for president, contribution limits established by the Federal Election Campaign Act (FECA) regulated the great majority of campaign donations. FECA permitted party officials to solicit uncapped contributions known as “soft money,” but such funds could only be spent on party-building activities such as voter registration drives.

Accordingly, a candidate needed a broad base of support among thousands of contributors to fund a competitive presidential campaign. When George Bush raised tens of millions in 1999, he locked up a critical mass of wealthy contributors and thus denied other Republican contenders the financial resources necessary to mount a viable primary campaign.

Citizens United has changed everything

But in January 2010, the campaign finance system changed dramatically when the Supreme Court decided Citizens United v Federal Election Commission. Citizens United turned on the question of whether the FEC could restrict campaign advertisements by independent political committees that do not coordinate their activities with candidates or parties. In a deeply divided opinion, a narrow majority of the justices ruled against the FEC. The ruling effectively exempted Super PACs and other independent groups from FECA’s contribution limits.

Campaign expenditures have skyrocketed ever since. The 2012 election cost an all-time record of $7 billion. The 2016 campaign will undoubtedly surpass that record.

The massive influx of Super PAC money has severely eroded the influence of the party establishment. Super PACs enable candidates to mount well-funded primary campaigns without any establishment support whatsoever. Indeed, in a post-Citizens United world, all a candidate needs in order to run for president is a billionaire willing to fund a Super PAC on the candidate’s behalf.

The new kingmakers in Republican politics

It’s no coincidence, therefore, that the 2016 campaign has attracted a record number of both candidates and billionaire-backed Super PACs. For example, the hedge-fund manager Robert Mercer has reportedly given $31 million to Super PACs supporting Ted Cruz. Home Depot founder Ken Langone has committed to raising millions of dollars on behalf of a Chris Christie Super PAC.

Las Vegas casino magnate Sheldon Adelson, who gave $93 million to Republican Super PACs in 2012, has voiced his support for Marco Rubio in 2016. The wealthy investor Foster Friess is backing a pro-Santorum Super PAC.

Most notable of all, Charles and David Koch have announced that they intend to spend almost $900 million on the 2016 election. Early signs indicate they like Scott Walker.

Thus, while Jeb Bush’s fund-raising numbers sound impressive by previous standards, his campaign war chest doesn’t scare anyone today. No candidate will monopolize Republican fund-raising in 2016. The flood of money unleashed by Citizens United means there is plenty to go around for everyone, including candidates openly hostile to the GOP establishment.

If Jeb Bush is to win the nomination, he’s going to have to do it by winning over rank-and-file Republican voters. The days when the party establishment could use its fund-raising powers to control the nomination process are long gone.